Electric-motor meter.



P. MAY.

ELECTRIC MOTOR METER.

APPLICATION FILED 112111.10, 1902;.

Patented May'23, 1911.

ZL z'bwsses J1: 1/611 Z'or mm Jditil', or cnnrmocrrnnnono, GERMANY.

ELECTRIC-MOTOR METER.

ease l0.

Specification of Letters Patent.

Patented May 23, 1911.

Application filed March 10, 1908. Serial No. 420,124.

catc at a small load loss than the correctreading; and no means hashitherto been provided by which in a manner resembling that of theauxiliary coil used in wait-hour meters, there can be produced anadditional torque 0t sullicicnt strength, to counteract the influenceofthc friction on the indications of the meter during the continuance ofthe low load.

Various attempts have been made by means of windings, armoured aroundthe permanent magnet or on a shunt of the same, through which thecurrent has bccniiassed, to vary' the field oi" the magnetin been dancewith the friction factor, but the 'el' cct of such compensating windirrs has in niost cases been but small or too large a quantity of copperhas been required to produce the desired rii'ect; while it has moreoverbeen impossible by these means toobtain an addilvJIlill'il'OQllG whilethe load remainedlom ow, my iimmtion relates to a (t mo hy means ofwhich ltl'NiCOYllPS possible to oly tain a greater proportional torquewlihn the load is low than in the case of a higher load. To obtain thiseffect I'rnakc use of. an ampere-hour meter consisting-of a ermanentmagnet and an armature rotating in its field, the armature beingconnected in series or in shunt Withthe circuit. The connection betweenthe armature and the circuit is'cffected by means of a commutator, themerits of which are dividedalong a helical line, so that, when thebrushes are moved axially along the commutator, the direction of thelines of forcclot the armature field is changed with regard to those ofthe field of the permanent magnet. I arrange the (301th mutritorsegments so, that the torque produced by a. current of certain strengthis a max mum when the brushes are nearest the u'mol'ure core and isdiminished when the hru nus are removed from the same. The brushes areprovided on one end of a twoarmed lever, on the other end ofiwhich isfastened a coil, through which the current passes and which isinfluenced by a permancnt magnet so as to move the brushes along thecommutator when the strength of the current will change.

M y invention will be best understood with reference to the accompanyingdrawings, in which like parts are signified by like figures and ofwhich- Figures 1 and 2 are diagrammatic views of two forms ofampere-honr-meters embodying 'my invention.

In Fig. l, M is a permanent magnet, in the field of which rotates anarmature which is connected in parallel with the resistance W. B and Bare the brushes, K is a commutator, P is a pole piece, which ispol"rized by the permanent magnet. The brushes are attached to atwo-armed lever H pivoted at D, one arm of which carries the coil S. Thecurrent is conducted to the coil S from the resistance W by means of thespring F. The end of the coil S is connected with the brush il the otherbrush, B, being connected by means of a line wire spring with the ot ierend of the resistance WV, the coil and the armature being consequentlyconnected in series. The proportions are so chosen that in the case of avery weak current such for instance as a current of only 1% 01" themaximum, the coil S will fail to act on the lever II. The segments ofthe commutator are helical and the pitch of the screw may be so chosenthat the commutating position ol? the armature varies in vproportionwith the height at which the brushes are caused to lie on the commutatorby the action ol the coil S.

in operation, when themaximum current asses through the resistance \V,the coil S draws the lever II down so far that a contact piece thereonmakes contact with the screw A, with the result that the brushes arecaused to assume a certain positionon the commutator, "while .theattractive force of the coil can be easily made suflicicntly great toretain the lever H in the contact position even when the currentstrength in the resistance W has'sunk, for example, to half of themaximum load. \Vithin these load limits the torque of the armaturedepends solely on the current which flows through it and on the constantfield of the permanent ma ct. Should the current in the resistancehowever, sink to below one-half of the maximum load the friction, in ameter of ordinary construction; Will begin prejudicially to efi'ect thecorrectness of the indica- I tions, and. the interference of frictionwill.

increase as the load decreases. E1, on the other hand, the meter isprovided with a device in accoi'dahce with this invention the armaturewill now obtain an additional torque Which increases with the diminutionof the load. This is due to the fact that below a certain load, sayone-halt Of-lll1% maximum, the coil S Will move slowly upward wheneverthe current in the resistance \V decreases, while the brushes B and Bwill consequently be caused to lie lower on the commutator and as aresult of the helical shape or the commutetorsegmentS, the relativeposition oi th e lines of force of the armature'field and the lines offorce of the permanent magnet in these low positions Will be morefavorable, and it may easily be seen that by suitably choosing theproportions of the effective parts the calibration curve of the metercanvIit-hout dificulty be kept 'within the limits oi 1% for each pointof the lead. Lfior the pin'pose of effecting a reliable start even atminimum loads such a device in connection with ampere-hour meters citeas great advantages it enables eeaeio the number of windings and theWeight of the armature to be reduced and the current flowing through thearmature to be diminished With the resultthat the commutator will besubjected to much less ear.

Fl 2 shows a dilierent method of connecting up the coil S, vvhich is inthis instaiipe connected in parallel. to the-armature.

What I claim and desire to be secured by Letters Patent is:

In an electric meter a permanent magnet for creating a field of force, arotatable armature in this field being connected in series relation withthe load, a commutator having segments these being divided along ahelical line, brushes connecting the commutator segments with thecircuit and arranged on a lever and means for turning the lever underthe influence of the strength of the current flowing in the loadcircuit.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing Witnesses.

PAUL MAY.

Witnesses;

JULIUS RUNELAND, Gurwonn Born mo.

